#include <stdio.h>
#include <stdlib.h>

/* ------------------------
   List element definition
   ------------------------ */
struct ListElem
{
   int              value;
   struct ListElem* next;
};

void printList( struct ListElem* h )
{
   while ( h != NULL )
   {
      printf(" %d\n", h->value );   	// Print

      h = h->next;			// Go to next element in list
   }

   printf("\n");
}


struct ListElem* insertHead(struct ListElem* head, struct ListElem* elem)
{
   elem->next = head;		// make "elem" point to "head"

   return(elem);		// return address of new head
}

struct ListElem* deleteHead ( struct ListElem* h )
{
   struct ListElem* deleted;
   struct ListElem* newHead;

   if ( h == NULL )
      return(NULL);        // Nothing to delete....

   deleted = h;            // Save the location of the deleted element
   newHead = h->next;      // We will return this value

   free(deleted);          // Un-reserve memory cells 
   return( newHead );      // Make the second element the new head      
}


int main(int argc, char *argv[])
{
   struct ListElem* head;   // Head of list
   struct ListElem* p;      // Help variable to allocate new list element

   head = NULL;           // Empty list

   /* ========================================================
      Insert 123
      ======================================================== */
   p = malloc( sizeof(struct ListElem) ); 
   p->value = 123;			
   head = insertHead( head, p);		

   /* ========================================================
      Insert 444
      ======================================================== */
   p = malloc( sizeof(struct ListElem) ); 
   p->value = 444;
   head = insertHead( head, p);		

   /* ========================================================
      Insert 789
      ======================================================== */
   p = malloc( sizeof(struct ListElem) ); 
   p->value = 789;
   head = insertHead( head, p);		

   printList(head);


   head = deleteHead( head );		
   printList(head);

}